In revenge of Batman deducing Riddler's hideout which led to his arrest, Edward Nigma set up in Arkham city a total of 400 challenges for the dark knight to solve. When Batman completes a certain amount of challenges, The Riddler will reveal one of his hostage's locations for Batman to find. Contrary to popular belief, the player does NOT have to finish all of the challenges to defeat Riddler. You need to solve about 380 of the 400 challenges. Challenges include finding Riddler trophies, answers to riddles, destroying TYGER security cameras, hacking TYGER mainframes, destroying certain objects such as Joker balloons or fake penguins, completing physical challenges, and interrogating Riddler's henchmen.